1. Field of the Invention
This invention relates to a signal reproducing apparatus and more particularly to tracking control to be performed in reproducing a signal from a recording medium on which a plurality of tracks are formed in parallel.
2. Description of the Related Art
Reproduction tracking control systems which have heretofore been proposed and practically used for home video tape recorders (hereinafter referred to as home VTRs) include a dedicated control track system called a CTL system and a 4fATF system. In the CTL system, a fixed magnetic head is arranged at a part of a tape path to record a vertical synchronizing periodic signal separately from a recording signal in the longitudinal direction of the tape. In the 4fATF system, a rotary head which records and reproduces a main signal is arranged to recurrently record pilot signals having four different relatively low frequencies in a state of being superimposed on the main signal in tracks in which the main signal is recorded and, at the time of reproduction, a tracking error signal (an ATF error signal) is obtained by comparing crosstalk components of the pilot signals which are reproduced from the two adjacent tracks on both sides of a mainly reproduced track.
It has recently become a general tendency to arrange home VTRs to give a high image quality and to digitally process signals. As a result, some home VTRs recently developed are arranged to be capable of recording and reproducing a relatively great amount of information by divisionally recording one frame amount of image signal in a plurality of tracks. Some new tracking control systems that are applicable to such VTRs are now being developed.
The new tracking control systems include a system, wherein two different pilot signal components are recorded in every other track in a state of being superimposed on the main recording signal (hereinafter this system will be referred to as a 2fATF system). The two different pilot signal components are superimposed by various methods. In one superimposing method, analog pilot signals are arranged to be mixed with the recording signal. In another method, a digital modulation process is controlled in such a way as to have the pilot signal eventually superimposed on the recording signal.
Further, tracking control systems arranged for a slow reproduction mode include an intermittent slow system whereby the tape is alternately caused to travel and to come to a stop and another system whereby the tape is caused to travel at a predetermined speed which is slower than a tape speed employed in recording.
However, according to the new tracking control system called the 2fATF system, the tracking error signal is obtained from only the pilot signals that are reproduced by some of heads. In a reproduction mode in which the tape is caused to travel at the same speed as the speed employed in recording, an effective tracking error signal can be obtained for every period of tracing. However, in the event of the slow reproduction mode in which the tape is caused to travel at a slower speed than the speed employed at the time of recording, the number of tracing steps which give effective tracking error signals decreases to deteriorate the performance of the tracking control system.
Further, in cases where a slow reproduction is performed by intermittently transporting the tape or where the tape is caused to start moving from a stopped state, some period of time is required before a stable tracking state is obtained without any dropout in a reproduced signal because, in such a case, the stopped position of the tape varies with the state of the apparatus or a speed at which the tape has been traveling before the stop. It is inevitable to have a reproduced image disturbed under such a condition either during the slow reproducing process or at the beginning of a normal reproduction.